Lift seat

ABSTRACT

A lift seat includes a seating surface, for example, a toilet seat, mounted on a supporting frame by a four-bar linkage. The four-bar linkage includes a lower link fixed to the frame and an upper link fixed to the seat. An armrest is attached to a front link of the four-bar linkage for pivoting therewith against the bias of the spring which loads the four-bar linkage as the seat is lowered from a raised position in a seating position. Energy stored in the spring is then available to lift the person from the seating position back to the raised position. A damper is connected to the four-bar linkage to prevent abrupt movement of the seat as the four-bar mechanism collapses and expands, while a gas spring is provided to initially resist movement of the four-bar linkage from either the expanded or the collapsed condition unless the armrest is initially rotated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S.application Ser. No. 07/926,430, filed Aug. 10, 1992, now U.S. Pat. No.5,312,157 which application is designated as a U.S. National Phase underPCT/US93/07476, filed 10 Aug. 1993, and is a continuation-in-part ofparent application Ser. No. 07/702,387, filed 20 Feb. 1991 nowabandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The instant invention relates to devices for assisting infirm or injuredindividuals to move from a standing position to a sitting position andfrom a sitting position to a standing position. More particularly, theinstant invention is directed to improvements chairs and toilet seatswhich are configured to assist infirm individuals in lowering themselvesto and raising themselves from the sitting position.

2. Prior Art

The patent literature includes numerous arrangements for assistinginfirm individuals in sitting down and standing up from a chair ortoilet seat.

U.S. Pat. No. 4,538,853 discloses a chair with a resilient mechanism forassisting an occupant in raising him- or herself to a standing position.The chair is provided with a seat cushion which pivots relative to thechair frame about an axis near the rearward edge of the frame. Themovement also serves to at least simultaneously partially elevate anarmrest. When the chair is occupied, resilient struts are compressed tostore energy for lifting the occupant. The seat may be manually lockedin its lowered position.

U.S. Pat. No. 3,975,051 discloses an orthopedic chair which includes amovably supported frame assembly which serves to maintain a forwardlyand downwardly extending saddle-shaped seat at a desired elevationbetween a pair of laterally spaced sidewalls and a backrest. The chairof this patent utilizes footrests and relies on electricity for itsoperation.

U.S. Pat. No. 3,473,174 discloses a power-driven, tilted seat in whichthe seat and associated armrests are fixed relative to one another andmove with respect to a supporting frame. Power-actuated hydrauliccylinders are used to raise and lower the seat. U.S. Pat. No. 4,587,678to Love also relies on an electrically driven hydraulic lift. However,in this patent, the armrests are fixed with respect to the frame, andonly the seat moves.

U.S. Pat. No. 4,907,303 discloses an orthopedic chair with aspring-loaded seat, wherein a coil spring is tensioned as a user sits inthe seat in order to store energy where it is subsequently used toassist in lifting the user to his or her feet when he or she wishes tostand.

A hand brake grips a cable attached to the spring to control applicationof the spring's force to the seat.

Each of the above-discussed patents are exemplary of prior artapproaches to the problem of providing chairs and seats for the infirm.However, none of these seats discloses arrangements wherein a seat notrequiring auxiliary power functions effectively for people over a widerange of heights and weights while effectively utilizing ergonomicprinciples in its design and operation to provide convenience, comfort,and security for its users.

SUMMARY OF THE INVENTION

In view of the aforementioned object, the instant invention contemplatesa lift seat for moving a person from an initial raised position to asubsequent lowered position for sitting and thereafter back to theinitial raised position to facilitate standing. The lift seat comprisesa seating surface upon which the person sits and applies a force; aframe for supporting the seating surface, and a four-bar linkage havinga lower link, an upper link, a front link, and a rear link with thefront and rear links pivoted to the upper and lower links, the lowerlink being secured to the frame and the upper link being attached to theseating surface; an armrest for supporting the person using the seat andfor initiating operation of the seat. The armrest being secured to oneof the links pivoted to the upper and lower links. A spring device iscoupled to the four-bar linkage and frame for resisting lowering of theseating surface from the raised to the lowered position and for storingenergy provided by the weight of the person sitting on the seat forsubsequently lifting the person from the lowered to the raised position.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features, and attendant advantages of the presentinvention will be more fully appreciated as the same becomes betterunderstood when considered in conjunction with the accompanyingdrawings, in which like reference characters designate the same orsimilar parts throughout the several views and wherein:

FIG. 1 is a perspective view of a lift seat in the form of a toilet seatconfigured in accordance with the principles of the instant invention;

FIG. 2 is a front view of the lift seat of FIG. 1;

FIG. 3 is a top view of the lift seat of FIG. 2;

FIG. 4 is a side view of the lift seat of FIG. 1, showing the lift seatin its raised position with the pivoted toilet seat shown in phantom;

FIG. 5 is a side view of the lift seat viewed from the opposite sidefrom FIG. 4;

FIG. 6 is a side view taken from the same side as FIG. 4, showing thelift seat collapsing to its lowered position;

FIG. 7 is a side view taken from the same side and FIGS. 4 and 6,showing the lift seat in its lowered position;

FIG. 8 is a side view similar to FIG. 7 showing initial forces necessaryto raise the seat;

FIG. 9 is a side view showing the seat rising to lift its occupant to araised position which-facilitates standing;

FIG. 10 is a side view showing the seat in its raised position;

FIG. 11 is a side view of an evolved embodiment of the inventionillustrating a preferred anchoring of a coil spring, increased spacingbetween the front and rear legs and a latch for holding the seat in itslowered position;

FIG. 12 is an enlarged side view of the latch shown in FIG. 11 with thelatch in the unlatched mode;

FIG. 13 is a view similar to FIG. 12 but showing the latch in a latchedmode;

FIG. 14 is an end view of the latch of FIGS. 12 and 13 showing the latchin the latched mode of FIG. 12;

FIG. 15 is an end view similar to FIG. 14 but showing the latch in anunlatched mode;

FIG. 16 is a front view of the lift seat illustrating a bucketattachment and bucket for bedside use as well as an optional back rest;

FIG. 17 is a top view of the lift seat of FIGS. 11 and 16 showing thebucket installed;

FIG. 18 is a side view of an additional embodiment of the inventionwherein the lift seat is configured as a chair and showing the chair ina raised mode;

FIG. 19 is a top view of a portion of the additional embodiment of theinvention showing a pair of dampers with a strut connected to anelastomeric spring disposed therebetween; and

FIG. 20 is a side view similar to FIG. 18 but showing the chair in alowered mode.

DETAILED DESCRIPTION

Referring now primarily to FIGS. 1-5, there is shown a lift seat,designated by the numeral 10, configured in accordance with theprinciples of the instant invention. In the illustrated embodiment, thelift seat 10 is positioned over a toilet bowl 11 and includes a toiletseat 12, which is mounted on a frame, designated generally by thenumeral 14, by a first and second four-bar linkages, designatedgenerally by the numerals 16 and 18. The four- bar linkages 16 and 18are Joined to one another by a rigid strut 19 so that the four-barlinkages move in concert with one another. A first armrest, designatedgenerally by the numeral 20, is fixed to the first four-bar linkage 16,and a second armrest, designated by the numeral 22, is fixed to thesecond four-bar linkage 18. The four-bar linkages 16 and 18 are coupledto one another by a rigid strut 19 so as to collapse and expand inconcert.

In operation, the toilet seat 12 is lowered from its raised positionshown in FIGS. 1-5 through an intermediate mode shown in FIG. 6 to alowered position shown in FIG. 7. As the toilet seat 12 is lowered fromits raised position to its lowered position of FIG. 7, the four-barlinkages 16 and 18 collapse.

The various elements of the lift seat 10 cooperate to provide a safe andconvenient device which facilitates lowering an infirm person from astanding to a sitting position. In the illustrated embodiment, the liftseat 10 is utilized with a toilet seat 12, however, the lift seat 10 maybe used for any type of chair.

The support frame 14 is rigid and is formed of first and second pairs ofU-shaped leg supports 24 and 26 connected by a front brace 28. The firstleg support 24 is shown in the side view of FIG. 4 and comprises a frontleg 30 and a rear leg 32 joined by a beam 34. The second leg support 26is shown in- the side view of FIG. 5 and comprises a front leg 36,joined to a rear leg 38 by a beam 40. The strut 28 joins only the frontlegs 30 and 36 proximate the floor upon which the support frame 14 restsso that the toilet bowl 11 may be received between the rear legs 32 and38. A U-shaped connecting bar 42 is connected to the first and secondbeams 34 and 40 of the U-shaped leg supports 16 and 18 by thread bolts44 and 46, which are received in slots 48 and 50 in the ends of theU-shaped bar 42. The U-shaped bar 42 includes a pair of slots 52 and 56,which receive the bolts which normally retain the toilet seat (notshown) ordinarily associated with the toilet bowl 11.

Referring now mainly to the side view of FIGS. 4-10, the four-barlinkages 16 and 18 disposed between the toilet seat 12 and the frame 14each include base links 60, which are fixed to the bars 34 and 40 of theU-shaped leg supports 24 and 26. Pivoted by pivots 61 to the front endsof the base links 60 are front links 62, which are fixed to the armrests20 and 22. Pivoted to the rear end of the base links 60 by pivots 64 arerear links 66, which cooperate with the front links 62 to determine theheight and attitude of the toilet seat 12. The front links 62 arepivoted to top links 68 by hinges 70, while the rear links 66 arepivoted to the top links 68 by hinges 72. The toilet seat 12 is fixed tothe top links 68, but, as seen in FIG. 3, the toilet seat pivots to thephantom position with respect to the top links 68. The armrests 20 and22, which are bolted or otherwise fixed to the front links 62 of thefour-bar linkages 16 and 18, each includes an upper rail 80 and a lowerrail 82, which is joined to the upper rail by U-shaped portions 84 and86. Fixed to the top rails 80 are grips 88, each having a raisedhand-stop portion 90. When the seat is in its lowered position, as shownin FIG. 7, the grips 88 are horizontal. Depending from the lower rail 82and rigid with respect to the armrest structures are struts 92, each ofwhich has a lug 94 thereon, with a eyelet 96 retaining a loop 98 forconnecting a coil spring 100 thereto. In the preferred embodiment, acoil spring 100 is attached only to the strut 92 of armrest 20. A secondend 102 of the spring 100 is attached to a loop 104 which, in turn, issecured to a hook 106. The hook 106 has a threaded shank 108 whichpasses through the rear leg 32 of the U-Shaped leg support 24. A nut 112on the shank 108 is used to adjust the tension on coil spring 100. As isseen in FIGS. 4 and 5, the coil spring 100 is untensioned when thetoilet seat 12 is in its raised position. It only becomes tensionedafter a person sits on the seat 12 and seat lowers, as is seen in FIG.6.

While in the raised position of FIG. 4, the seat 12 is held biased toits fully raised position by a gas spring 120, which has a projectingrod 122 pivoted to a bracket 124 fixed on the rear link 66 and a pistonrod 126 pivoted on a bracket 128 mounted on the rear leg 32 of theU-shaped support leg 24. In the preferred embodiment of the invention,only a single gas spring 120 is used in conjunction with the coil spring100.

Secured to the other rear link 66 (FIG. 5) is a damper 140, the cylinderof which is pivoted to a bracket 142 affixed to the rear link 66 and apiston rod 144 of which is pivoted to a bracket 146 fixed on the rearleg 38 of the U-shaped leg support 26.

The gas spring 120 holds the four-bar linkages 16 and 18 in the expandedposition of FIGS. 1-4 by causing flanges (dotted lines 150), which arefixed to struts 92, to engage bottom surfaces of the base links 60. Inthis way, the four-bar linkages 16 and 18 are normally prevented fromcollapsing in the forward or rearward direction against the bias of thegas spring 120, the coil spring 100, and the damping strut 140.

In operation, when the user approaches the lift seat 10, the user maysupport him- or herself by grasping the U-shaped connecting portions 84of the armrests 20 and 22 while facing the lift seat.

When in this position, the user applies force to the armrests in thedirection of arrow 160. This induces torque in the armrests 20 and 22 inthe direction of arrow 162 about pivot point 61. The torque in thedirection of arrow 162 causes the flanges 150 extending inwardly fromthe strut 92 to abut the base link 60, providing a rigid, stable supportfor the person facing the lift seat 10 When the person turns around andfaces away from the lift seat 10, the person can still support himselfon the U-shaped connecting position 80. When one sits on the seat 12while the seat is in the raised position of FIGS. 1-5, the seat does notinitially sink toward its lowered position of FIG. 7 but, rather,remains in the raised position. This is because the four-bar linkages 16and are prevented from collapsing due to the gas spring 120 and thedamping strut 140 holding the rear links 66 in the expanded position inwhich the vertical component induced in the four-bar linkages 16 and 18by a person's weight applied in the direction of arrow 164 tends to pullthe rear link 66 forward in the direction of arrow 166. In other words,the force 164 of the person's weight tends to rotate the rear link 66about the pivot 64 in the counterclockwise direction in FIG. 3,exemplified by the arrow 168. These forces are applied through the toplink 68 and downwardly in the direction of the arrow 170 in the frontlink 62, which links 62 are fixed to the bottom rail 82 of the armrests20 and 22. The armrests 20 and 22 tend to rotate in the direction ofarrow 162 and press the stop plate 150 against the bottom of base link60 as long as force is applied with a resultant component in thedirection of arrow 60. This is, however, a fine balance, which, as willbe explained hereinafter, is easily overcome by the person sitting onthe toilet seat 12 or by a helper.

In order to lower the seat 12 with a person sitting thereon, the personovercomes the static relationship established by the four-bar linkages16 and 18 by applying a slight force in the direction of arrow 200 (seeFIG. 4). This is accomplished by simply moving one's hand forward on theU-shaped connecting portion 84, applying a very slight pressure at anarea 202 on the rail 80. As is best seen in FIG. 6, this slight pressurecauses the armrests 18 and 20 to pivot in the direction of arrow 204about pivot point 61. Since the bottom rails 82 are fixed to the frontlink 62 of the four-bar linkages 16 and 18, a force in the direction ofarrow 206 is applied through the upper links 68. This force 206 tends toshift the force component 164 (see also FIG. 4) provided by the user'sweight slightly over center with respect to the gas spring 120 so thatinstead of the gas spring 120 being pulled to extend (which the gasspring cannot do), the gas spring is moved slightly over center so thatit is positioned by the rear link 66 to collapse under the force 164 ofthe person's weight. When the gas spring 120 is positioned to collapse,the piston rod 126 slides into the cylinder, compressing gas in thecylinder 125 and storing that energy in the gas spring for subsequentuse.

The damper 140 (see FIG. 5) is positioned on the opposite side of thechair, as shown in FIGS. 4 and 6, and initially operates insubstantially the same fashion as the gas spring 120. In other words,the damper 140 initially holds the rear link 66 in a position such thatthe weight component 164 of the person sitting on the toilet seat 12pulls the damper in extension. Again, when the armrest 22 is rotated inthe direction of arrow 204 (also see FIG. 6) about the pivot 61, thedamper 140 is rotated slightly in the direction of arrow 210 so as to goover center and allow the weight of the person on the seat 12 tocollapse the damper so that the piston on the end of piston rod 144slides into the cylinder 145.

As is seen in FIGS. 4 and 5, the coil spring 100 is initially slack.However, as the four-bar linkages 16 and 18 begin to collapse, the coilspring 100 is tensioned, as is seen in FIG. 6. The coil spring 100thereafter resists rotation of the armrests 20 and 22 in the directionof the arrow 204 and stores the energy imparted by force component 164due to the weight of the person sitting on the seat 12. When the seat 12reaches its completely collapsed position, as shown in FIG. 7, thespring 100 has stored a substantial portion of the energy imparted bythe person sitting on the seat 12. This partial energy is available tohelp lift the person back to the standing 10 position. While the coilspring 100 is completely tensioned in FIG. 7, the gas spring 120 isagain over center, only this time, it is exerting a force tending tokeep the four-bar linkages 16 and 18 collapsed. This provides a slightforce which must be overcome in order to feed the energy of the spring100 back into the system to start rotation of the armrest 120 in thedirection 220, as shown in FIG. 8.

Referring now more particularly to FIGS. 8, 9, and 10, when the personwishes to stand up, a slight force 224 is applied against theprojections 90 on the grips 88 to start the armrests 20 and 22 rotatingin the direction of arrow 220. This initially slightly lifts the frontlink 62 which, in turn, pulls the top link 68 via the connectionprovided by the hinge 70. The tension in top link 68 causes the rearlink 66 to begin rotating about the hinge 64 which, in turn, lifts theupper end of gas sparing 120 over center so that the gas spring 120 nowapplies its force to expand the four-bar linkage 16 rather than tocollapse the four-bar linkage 16. The coil spring 100 is alreadyapplying a force in the direction of arrow 228, which force is added tothat of the gas spring 120. The user then leans slightly forward toshift his or her weight slightly forward, and the energy stored in coilspring 100 and gas spring 120 lifts the seat 12 with the person sittingthereon smoothly through the intermediate position of FIG. 9 to thefinal position of FIG. 10, a position from which the person can easilystand.

In order to prevent the springs 100 and 120 from applying their forcetoo rapidly, the damper 140 (see FIG. 5) resists rapid movement of therear links 66 from the FIG. 8 position through the FIG. 9 position tothe FIG. 10 position.

As is seen in FIG. 4, the toilet seat 12 has a pair of pads 240 on thebottom surface 242 thereof. The pads 240 abut the top surface of the toplink 68 in the four-bar linkages 16 and 18. The attitude or angularorientation of the seat 12 with respect to the horizontal can,therefore, be controlled to lift the seat slightly so as to accommodatetaller individuals or so as to lower the seat. Since the seat 12 ispivoted on the upper links 68, adjustment of its height by determiningthe angle that it forms with the upper links is easily accomplished bylifting the seat up and changing the thickness of the pads 240.

By the interaction and cooperation of the gas spring 120, the coilspring 100, and the damper 140 with the four-bar linkages 16 and 18joined by the strut 19, the toilet seat 12 moves between its raised andlowered position with a smooth, unabrupt motion. The armrests 20 and 22allow the person using the seat to initially brace him- or herself andthen to initiate lowering and raising of the toilet seat 12 by exertingminimal effort. A lift seat is, therefore, provided which assists infirmindividuals in both standing and sitting.

Referring now to FIGS. 11-17, there is shown an evolved embodiment ofthe instant invention wherein the original lift seat 10, now designatedby the general reference numeral 300, is configured so as to be suitablefor bedside use as well as for use with a toilet 11 (see FIG. 1). In theembodiment of FIG. 11, the front legs 302 and 304 and rear legs 306 and308 are spaced further apart than in the embodiment of FIGS. 1-10. Inthe embodiment of FIGS. 1-10, the pair of front legs 30 and 38 and thepair of rear legs 32 and 36 are spaced about 201/2 inches apart whereas,in the embodiment of FIGS. 11-16, the pair of front legs 302 and 304 arespaced about 251/2 inches from the pair of rear legs 306 and 308. Thisprovides a more stable Support for the lift seat 300 so that the liftseat 300 is readily used with or without the toilet 11. In theembodiment of FIG. 11, the bar 42 is no longer necessary since it is notnecessary to bolt the lift seat 300 to a toilet in order to have astable lift seat.

Referring now to FIGS. 16 and 17, it is seen that a bucket 310 issupported beneath the toilet seat 12 by a plastic covered wire bracket312. The plastic covered wire bracket 312 has portions 314 and 316 whichfit beneath an annular lip 320 of the bucket 310. The wire bracket 312also has a U-shaped portion 322 which has a cross-piece 324 that fitsbeneath the bucket 310 to support the bucket from the bottom while across-piece 326 underlies the lip 320 to support the bucket at the top.Front and rear struts 330 and 332 engage with the side frame members 334and 336 to support the bracket 312. The bracket 312 is readily removablewhen one needs to utilize the lift seat with a toilet such as the toilet11 of FIG. 1.

In the embodiment of FIGS. 11, 16 and 17, two coil springs 100 areutilized, one positioned on each side frame 24 and 26 of the lift seat300 whereas in the embodiment of FIGS. 1-10 only a single coil spring100 is used.

As is seen in FIGS. 11 and 17, the horizontal cross-pieces 334 and 336joining the legs of the seat 300 each have a spring anchor 340 thereon.The spring anchors 340 each have three slots 342, 344 and 346 therein.Received in one of the slots of each anchor 340 is a rectangular loop347 which is attached to ends 348 of the springs 100.

In order to prevent the four-bar linkages 16 and 18 from collapsingcompletely, triangular blocks 349 are inserted between the four-barlinkages 16 and 18.

In the embodiment of FIGS. 11-17, the additional features of having theblock 340 for adjusting the tension on two springs 100, placing thefront legs 302 and 304 a further distance from the rear legs 306 and308, as well as providing bracket 312 to support the bucket 314, enhancethe lift seat 300 to make it even more responsive to patients of variousweights and to allow bedside use wherein bucket 314 can be used. As isseen in FIG. 16, a back rest 380 may be added to the toilet seat 12.

The latch 350 of FIGS. 11-15 enables the caregiver or nurse to keep thepatient seated until the nurse or caregiver is ready for the patient torise. Having the disclosed latch 350 provides a degree of complexity sothat an infirm patient may have difficulty unlatching and latching thechair and thus the caregiver has some degree of control over thepatient.

Referring now specifically to FIGS. 12, 13 and 14, the latch 550 forlatching the seat in the down position of FIG. 11 is shown in detail.The latch 350 is fixed to the lower rail 352 of the arm 20 (see FIG. 1).The latch 350 is comprised of a block 354 with a bore 356 therethroughin which is received an L-shaped latching pin 358. The L-shaped pin 358has a shank 360 and a handle 362. When the latch is in the latchedposition, the shank 360 projects through a hole 364 in an L-shapedbracket 366 which is mounted to the frame 336 of the chair. When thelatch is unlatched, the latching pin 358 is moved from the position ofFIG. 14 to the position of FIG. 15 where the shank 360 is removed fromthe opening 364 in the L-shaped bracket 366. In order to hold the pin358 in the latched position, the block 354 has a cutout 370. The cutout370 is behind an angled wall 372 which holds the latch pin 358 in thelatched position of FIGS. 13 and 14 but which allows the handle 358 tobe rotated clockwise with respect to FIGS. 12 and 13. By rotating thehandle 358 clockwise, it clears the wall. 372 and can be slid in theaxial direction with respect to the shank 360 to the open position. Whenthe handle 358 is then released, the handle is outside of the angledwall 372 as is seen in FIGS. 12 and 15 so as to not lock with theL-shaped bracket 366. Upon lowering the chair, the handle 362 can berotated to clear the wall 372 and then pushed so that the shank 360enters the opening 364 through the. L-shaped bracket 366. Upon againreleasing the handle, the handle falls behind the wall 372 and is lockedas is shown in FIGS. 13 and 15.

Referring now to FIGS. 18, 19 and 20, there is shown another embodimentof the invention wherein the invention is used as a regular chair whichmay be in a form similar to a lounge chair. In this embodiment, theframe members are substantially similar to the frame members of FIG. 1as are the collapsible four-bar mechanisms 16 and 18. As is seen in FIG.19, disposed between the four-bar linkages 16 and 18 are a pair ofdampers 402 and 404. As is seen in FIGS. 18 and 20, the dampers 402 and404 are pivoted at one end to the bottom links 60 of the four-barlinkage or to a cross-piece 405 rigid with the bottom links 60 and atthe other end to the bottom of seat 440 which is rigid with top links 68of the four-bar linkage. As the four-bar linkages 16 and 18 collapse andrise, the dampers 402 and 404 will provide damping and thus smooth theaction.

Disposed between the dampers 402 and 404 is an arm 410. The arm 410 hasa roller 412 at its upper end which engages the bottom surface of theseat 440 which is rigid with the links 68. The bottom end of the roller412 is pivoted at pivot pin 414 to an annular elastomeric spring 415available from the B. F. Goodrich Co. The annular elastomeric spring 415has an outer casing 416 which is anchored by struts 418 and 420 to aplate 424 extending between the upper rails 34 and 40 of the side frames24 and 26. Within the outer casing 416 there is a ring of elastomericmaterial 428 which is fixed to the outer ring 416 by a tab 430 of theelastomeric material. The elastomeric material 428 is bonded to an innerring 432 to which the strut 410 is pivoted at the pivot pin 414.

The seat 440 is divided into first and second portions 442 and 444 whichhave pads 446 and 448 thereon. The second seat section 444 is pivoted tothe first seat section 442 by a hinge 450. A strut 452 disposed betweenthe front legs 30 and 38 of the chair 400 engages the bottom surface ofthe second seat portion 444 to support the second seat portion when thechair 400 is in the raised mode. The back rest 454 is mounted on theframe 14 of the chair by a resilient vertical strut 456. The back rest454 has a padded portion 458 at the top thereof. Alternatively, the backrest 454 can be mounted on the rear of the first seat portion 442 of thechair with the strut 456 bolted thereto.

When a person sits in the chair 400, the chair collapses from the FIG.18 to the FIG. 20 position, causing the dampers 402 and 404 to extendand the roller 412 on the strut 410 to roll along the bottom of thefirst seat portion 442 of seat 440. As the roller 412 rolls on thebottom of the first seat portion 442, the inner portion 432 of theelastomeric spring 414 rotates with respect to the outer portion 416deforming the elastomeric material 428 and storing energy therein. Thecombination of the dampers 402 and 404 and deforming the elastomericmaterial 428 allows the seat 442 to lower gradually from the FIG. 18 tothe FIG. 20 position. As this happens, the second portion of the seat444 engages the backs of the person's thighs and pivots from theorientation of FIG. 18 to the substantially horizontal orientation ofFIG. 20, thus providing full seating support for the occupant.

When the occupant decides to rise, pressure is placed against thehandgrips 90 by the occupant and the occupant leans slightly forward,shifting weight on the first portion 442 of the seat. The deformedelastomeric material 428 is applying sufficient force to the strut 410material to cause the roller 412 to roll against the bottom surface ofthe first seat portion 442, thus lifting the seat and its occupant fromits FIG. 20 position back to its FIG. 18 position. As this happens, thesecond portion 444 of the seat pivots down, allowing the occupant tosubstantially straighten his or her legs in preparation for rising tothe fully standing position.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

I claim:
 1. A lift seat for moving a person from an initial raisedposition to a subsequent lowered position for sitting and thereafterback to the initial raised position to facilitate standing, the liftseat comprising: a seating surface upon which the person sits andapplies a force due to the weight of the person; a frame for supportingthe seating surface; a linkage movable between a raised and loweredorientation, comprising first link means pivoted at one end to the seatand at another end to the frame and second link means spaced from thefirst link means, pivoted at one end to the seat and at another end tothe frame; armrest means for supporting the person using the seat andfor initiating operation of the seat, the armrest means being secured toone of the links; and spring means coupled to the linkage and frame forresisting lowering of the seating surface from the raised to the loweredposition and for storing energy provided by the weight of the personsitting on the seat for subsequently lifting the person from the loweredto the raised position, the spring means comprising an annularelastomeric spring connected to an arm which engages the seat wherein asthe seat collapses, the arm deforms the spring by twisting the spring tostore energy therein.
 2. The lift seat of claim 1, wherein the firstlink means is comprised of a pair of spaced front links, and the secondlink means is comprised of a pair of spaced rear links, the links beingcoupled to operate in unison.
 3. The lift seat of claim 2, furtherincluding damper means coupled to the linkage for resisting movement ofthe linkage from a raised to a lowered position and from the lowered tothe raised position.
 4. The lift seat of claim 3, further including stepmeans for preventing the linkage from collapsing in a first directionand for allowing the linkage to collapse in a second direction oppositethe first direction.
 5. The lift seat of claim 3, wherein the armrestmeans comprises a pair of armrests on opposite sides of the seatingsurface, the armrests being fixed to the front links and being pivotedtherewith and wherein the spring means comprises a coil spring connectedat one end to the frame and at the other end to the armrest, wherebywhen the armrest moves from a first position corresponding to the seatbeing raised to a second position corresponding to the seat beinglowered, the spring is tensioned.